Rectifiers for AC to DC conversion of high frequency signals have been well known for decades. A particular type of diode rectifier when coupled to an antenna, called a rectenna, has also been known for decades. More specifically, over 20 years ago, Logan described using an array of rectennas to capture and convert microwaves into electrical energy in U.S. Pat. No. 5,043,739, granted Aug. 27, 1991. However, the dimensions of the antenna limited the frequency until recently, when Gritz, in U.S. Pat. No. 7,679,957, granted Mar. 16, 2010, described using a similar structure for converting infrared light into electricity, and Pietro Siciliano suggested that such a structure may be used for sunlight in “Nano-Rectenna For High Efficiency Direct Conversion of Sunlight to Electricity,” by Pietro Siciliano of The Institute for Microelectronics and Microsystems IMM-CNR, Lecce (Italy).
Still, the minimum dimensions required for such infrared light rectennas are generally in the microns. While these dimensions can be accomplished by today's masking technology, such processing is typically more expensive than the current solar cell processes, which require much larger dimensions.
Still, as Logan pointed out in U.S. Pat. No. 5,043,739, the efficiency of microwave rectennas can be as high as 40%, more than double that of typical single junction poly-silicon solar cell arrays, and when using metal-oxide-metal (MOM) rectifying diodes, as Pietro suggests, no semiconductor transistors are needed in the array core.
As such, it may be advantageous to be able to utilize the existing processing capability of current semiconductor fabrication without incurring the cost of such manufacturing.
Also, recently, Rice University reported that their researchers created a carbon nanotube (CNT) thread with metallic-like electrical and thermal properties. Furthermore, single-walled carbon nanotube (SWCNT) structures are becoming more manufacturable, as described by Rosenberger et al. in U.S. Pat. No. 7,354,977, granted Apr. 8, 2008. Various forms of continuous CNT growth may have also been contemplated, such as Lemaire et al. repeatedly harvesting a CNT “forest” while it is growing, in U.S. Pat. No. 7,744,793, granted Jun. 29, 2010, and/or put into practice using techniques described by Predtechensky et al. in U.S. Pat. No. 8,137,653, granted Mar. 20, 2012. Grigorian et al. describes continuously pushing a carbon gas through a catalyst backed porous membrane to grow CNTs in U.S. Pat. No. 7,431,985, granted Oct. 7, 2008.